Our goal is to understand the mechanisms involved in prolactin biosynthesis by the pituitary. In particular, we are concerned with the mRNA for preprolactin and its regulation. We hope to purify the preprolactin mRNA and then make its cDNA with reverse transcriptase. This will then be used as a probe for hybridization studies and attempts to study gene transcription. We will use pituitary tissue from rats, sheep and cattle as sources of RNA and DNA. The sheep and cattle tissue, obtained at slaughter, provide a large source of nucleic acid and can also be used in cell culture work. The effect of estrogen on preprolactin mRNA accumulation and its gene transcription will be studied. Attempts will be made to develop cell culture systems in which estrogen controls prolactin synthesis. Development of such cell cultures will permit a detailed study of regulation of the expression of the prolactin gene.